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Mixed models are powerful tools for the analysis of clustered data and many extensions of the classical linear mixed model with normally distributed response have been established. As with all parametric models, correctness of the assumed model is critical for the validity of the ensuing inference. Model robust regression techniques predict mean response as a convex combination of a parametric and a nonparametric model fit to the data. It is a semiparametric method by which incompletely or incorrectly specified parametric models can be improved through adding an appropriate amount of a nonparametric fit. We apply this idea of model robustness in the framework of the linear mixed model. The mixed model robust regression (MMRR) predictions we propose are convex combinations of predictions obtained from a standard normal-theory linear mixed model, which serves as the parametric model component, and a locally weighted maximum likelihood fit which serves as the nonparametric component. An application of this technique with real data is provided. / Ph. D.

This dissertation focuses on contextual frames that influence how consumers perceive prices and how that in turn affects their product evaluations and consumption decisions. This research consists of three essays and attempts to further the understanding of contextual factors that affect how consumers perceive prices (essay 1) and how perceptions about prices influence product inferences (essay 2) and decision making (essay 3). While there is a substantial body of research on price framing and price perception, my research identifies and attempts to fill some important gaps in the existing research. In my first essay, I introduce a new price framing effect – the upper limit framing effect. This essay shows that framing the upper limit of a price estimate as less than vs. not more than can result in systematic differences in perceptions regarding the underlying price. This research contributes to the existing price framing research, which primarily focuses on set prices, by investigating price estimates. It also makes important contributions to the temporal and monetary costs and semantic framing literatures and to the literature on negations. In my second essay, I contribute to the existing perceived price-quality research that primarily concerns only the market prices. This essay shows that consumers over-apply the perceived price-quality heuristic when setting product prices by themselves (self-decided prices). Specifically, this research shows that contextual factors that affect self-decided prices in turn influence product inferences, with the relationship between contextual frame and product inferences being mediated by self-decided prices. In my third essay, I contribute to the existing price framing research by showing that in the context of multiple price presentation, the price presentation order (ascending vs. descending) affects the perceived importance of price in the decision making – an effect I term as the price order effect – an effect that is explained by prospect-theory driven loss aversion. Specifically, this research shows that descending (vs. ascending) price presentation order results in significantly lower perceived importance of price in the decision making process which in turn influences subsequent consumption decisions. In addition to the individual contributions of each essay, this dissertation makes an overall contribution to the price framing and price perception research by identifying new price framing effects and by furthering the understanding of how consumers perceive prices and how perceptions about price influences consumer decision making. / Doctor of Philosophy / This dissertation shows how different contexts can influence consumers’ perceptions about product prices. Utilizing a variety of everyday consumption products and scenarios, we show new and interesting ways in which seemingly unrelated contexts and frames can influence price perceptions. Specifically, we show that novel contexts and frames can affect (a) how consumers perceive price magnitude (essay 1), (b) how perceptions about prices influences product inferences (essay 2), and (c) how important a factor is price perceived to be in the decision making process (essay 3). Essay 1 shows that framing the upper limit of a cost estimate as (“less than” vs. “not more than”) results in different perceptions about the underlying cost. Essay 2 shows that counter to intuitive expectations, consumers utilize prices that they themselves decide to pay for a product as being indicative of its quality. Essay 3 shows that ascending vs. descending price orders results in different consumption decisions due to differential perceived importance of price in the decision making. This dissertation also discusses the several important contributions made by this research.

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Indiana University-Purdue University Indianapolis (IUPUI) / Introduction: Regenerative endodontic therapy in immature teeth with necrotic pulps triggers continued root development thereby improving the prognosis of these teeth. Several agents are under consideration for the disinfection and conditioning phases of this therapy. Triple antibiotic paste (TAP, i.e. equal parts of ciprofloxacin, metronidazole, minocycline) is used for canal disinfection and 17% EDTA solution is used for dentin conditioning. However, TAP and EDTA cause demineralization and their effect on surface loss and surface roughness of radicular dentin during regenerative procedures has not been quantified. Surface loss may be correlated with reduced tooth strength and surface roughness may be correlated with stem cell attachment. Objectives: The aim of this in vitro study was to quantitatively investigate the surface loss and surface roughness on human radicular dentin after treatment with two concentrations of TAP followed by EDTA. Materials and Methods: Human radicular dentin specimens were prepared from extracted human anterior teeth and randomized into six experimental groups. Group 1: saline control; Group 2: 17% EDTA; Group 3: TAP 1 mg/mL; Group 4: TAP 1 mg/mL and 17% EDTA; Group 5: TAP 1,000 mg/mL; Group 6: TAP 1,000 mg/mL and 17% EDTA for 5 minutes. After TAP is applied to Groups 3-6, all groups were incubated for 4 weeks. Then, groups 2, 4, and 6 were treated with EDTA for 5 minutes. Dentin surface loss (μm) and surface roughness (Ra, μm) were quantified after various treatments using non-contact and contact profilometry, respectively. Data were analyzed by one-way analysis of variance (α = 0.05) Hypothesis: It was hypothesized that there would be a significant difference in surface loss or surface roughness between at least two treatment groups. Results: All treatment groups showed significantly higher surface loss compared to untreated control. Dentin treated with 1g/mL TAP caused significant increase in surface loss and surface roughness compared to dentin treated with 1 mg/mL TAP. However, only 1g/mL TAP treated dentin showed significantly higher surface roughness compared to untreated control. The use of EDTA after both concentrations of TAP did not have significant additive effect on surface loss and surface roughness of dentin. Conclusion: The use of 1 mg/mL TAP can minimize surface loss and surface roughness of radicular dentin compared to higher concentrations. The use of EDTA after TAP may not cause additional surface loss and surface roughness of dentin.

Master of Science / Department of Statistics / Paul I. Nelson / The variance of a response in a one-way random effects model can be expressed as the sum of the variability among and within treatment levels. Conventional methods of statistical analysis for these models are based on the assumption of normality of both sources of variation. Since this assumption is not always satisfied and can be difficult to check, it is important to explore the performance of normal based inference when normality does not hold. This report uses simulation to explore and assess the robustness of the F-test for the presence of an among treatment variance component and the normal theory confidence interval for the intra-class correlation coefficient under several non-normal distributions. It was found that the power function of the F-test is robust for moderately heavy-tailed random error distributions. But, for very heavy tailed random error distributions, power is relatively low, even for a large number of treatments. Coverage rates of the confidence interval for the intra-class correlation coefficient are far from nominal for very heavy tailed, non-normal random effect distributions.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

This research initiated an investigation of the structural relationships between melanocyte stimulating hormone (α-MSH) and its melanin dispersion on lizard (Anolis carolinensis) and frog (Rana pipiens) skins bioassays as representing models for mammalian and amphibian melanocytes, respectively. From previous extensive structure-activity relationships of α -MSH together with the theoretical modeling we were able to design a group of linear and cyclic peptides related to "4-10" fragment analogues of α -MSH. The solid phase synthesis of α -MSH and its related analogues using the p-methyl-benzhydrylamine resin was accomplished. The C-terminal carboxamide and N-terminal acetylamide were maintained in all peptides synthesized. The cyclic peptides were prepared in solution phase using the linear peptides generated by solid phase. All the cyclization were done by using the hydrochloride salts of the peptide and DMF as solvent with diphenylphosphoryl azide (DPPA) as a coupling reagent in the presence of K₂HPO₄ as a base. The yields of the cyclic peptides were in the range of 30-40 percent. In all the synthesized peptides the replacement of D-Phe⁷ with L-Phe⁷ causes reduction in the potency of the peptide on lizard or frog skins bioassays. Also, the reduction or increase in ring size in the cyclic peptide from a 23 membered ring diminishes the biological effect of the peptide under testing.

Dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science. Johannesburg, 2013. / The evolutionary genesis and the current adaptive significance of the use of the discontinuous gas exchange cycle (DGC) for respiration by insects is the subject of intense debate. Most current research centers on three adaptive hypotheses and one non-adaptive hypothesis; these are the hygric hypothesis, the chthonic hypothesis, the oxidative-damage hypothesis and the emergent-property hypothesis respectively. Workers of the harvester termite, Hodotermes mossambicus were selected as a model to test three of these hypotheses. The respiratory patterns of workers, investigated using flow-through respirometry, were obtained at 0 % relative humidity (RH), 100 % RH, at 100 % O2 and under varying temperature to evaluate the assumptions of the various hypotheses. A change in ambient humidity had no impact on metabolic rate (VCO2), coefficient of variation (CV) or the pattern of gas exchange but only influenced the amount of water loss experienced by workers. Major workers exposed to hyperoxia (100 % O2) responded by increasing spiracular control and constriction through the use of cyclic gas exchange thereby protecting their interior against the toxic effects of O2. As VCO2 increased in response to increasing temperature, the gas exchange pattern displayed by workers transitioned from a modified DGC through cyclic to continuous gas exchange. A true DGC, defined as showing all three phases and a CV value close to 2, was not expressed under any of the experimental conditions. The results of this study support the oxidative-damage and emergent-property hypotheses but not the hygric hypothesis. The workers of H. mossambicus spend only brief periods above ground before returning to the refuge of their underground nests and as such there is probably little selective advantage to the DGC for limiting respiratory water loss. The conclusion drawn from the study of termite workers is that changes in respiratory patterns are most likely an emergent property of the insects’ nervous and respiratory systems and spiracular control also serves to limit oxidative damage.